(1) Field of the Invention
The present invention relates to methodology and apparatus for forming thin film hydrogenated amorphous material, for example, hydrogenated amorphous silicon, hydrogenated amorphous carbon, hydrogenated amorphous silicon carbide and thin film transistor (TFT) material.
(2) Description of the Related Arts
Thin film hydrogenated amorphous materials, particularly materials formed from hydrogenated amorphous silicon (hereinafter referred to as a--Si:H) are widely used as electrophotographic photosensitive members for electrophotographic apparatus to form images upon irradiation with an information light beam since such materials have excellent durability and are not sources of environmental pollution.
As shown in FIG. 1, a photosensitive member consists of a blocking layer 103 for carrier injection a carrier generation and transport layer 104 and a surface protecting layer 105 layered sequentially onto a conductive substrate 100 such as aluminum (Al).
Blocking layer 103 for carrier injection is formed from a P type or N type a--Si:H, a--SiO:H, a--SiC:H or a--SiN:H material, and photosensitive layer 104 is formed from an a--Si:H material. The surface protecting layer 105 is made from a--SiC:H, a--SiN:H o a--SiC:H:F. Particularly, for the surface protecting layer 105, an a--SiC:H or a--SiN:H material having a wide band gap is used but a--SiC:H is superior from a hardness viewpoint.
However, Si in the surface layer reacts with oxygen in the air to form SiO which is hydrophilic and blurring may thus result under high humidity conditions.
Therefore, in the past the photosensitive materials have been heated or films which do not contain Si in the surface layer have been employed.
However, in cases where the photosensitive member is heated, it is necessary to include a heating source in the electrophotographic apparatus, thereby complicating the configuration of the electrophotographic apparatus and increasing its cost.
On the other hand, when the surface layer does not include Si, light transmissivity, hardness and suitability for use as a photosensitive member are diminished.